package com.hmdp.utils;

import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;

import java.util.Collections;
import java.util.UUID;
import java.util.concurrent.TimeUnit;

public class SimpleRedisLock implements ILock{

    private String name;
    private StringRedisTemplate stringRedisTemplate;

    public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {
        this.name = name;
        this.stringRedisTemplate = stringRedisTemplate;
    }

    private static final String KEY_PREFIX="lock:";
    private static final String ID_PREFIX = UUID.randomUUID().toString()+"-";//获取当前线程
    private static final DefaultRedisScript<Long> UNLOCK_SCRIPT;//加载lua脚本
    static{//静态代码块
        UNLOCK_SCRIPT = new DefaultRedisScript<>();
        UNLOCK_SCRIPT.setLocation(new ClassPathResource("unlock.lua"));
        UNLOCK_SCRIPT.setResultType(Long.class);
    }

    @Override
    public boolean tryLock(long timeoutSec) {
        //获取线程标识
        String threadId = ID_PREFIX + Thread.currentThread().getId();
        //获取锁
        Boolean success = stringRedisTemplate.opsForValue()
                .setIfAbsent(KEY_PREFIX+name, threadId, timeoutSec, TimeUnit.SECONDS);
        return Boolean.TRUE.equals(success);//包装类Boolean转为boolean可能出现空指针，使用Boolean.TRUE.equals()防止空指针问题
    }

    @Override
    public void unlock() {//调用lua脚本，保证操作的原子性
        stringRedisTemplate.execute(
                UNLOCK_SCRIPT,
                Collections.singletonList(KEY_PREFIX+name),
                ID_PREFIX + Thread.currentThread().getId()
        );
    }

    /*
    @Override
    public void unlock() {//分多步执行，容易出现线程问题，导致误删
        //获取线程标识
        String threadId = ID_PREFIX + Thread.currentThread().getId();
        //获取锁中的标识
        String id = stringRedisTemplate.opsForValue().get(KEY_PREFIX + name);
        //判断标识是否一致
        if(threadId.equals(id)){//判断完成后释放锁之前可能出现线程问题，导致误删
            //释放锁
            stringRedisTemplate.delete(KEY_PREFIX+name);
        }
    }
     */
}
